Besides drawn stuff, I think for some bands a good photograph or just some illustrative graphics used in a well design can make up for a nice cover as well
I also like the kind of things Bone Awl is doing with their covers.

Blood Ritual "Black Grimorie"
Drawn and Quartered all of them.... they are all done by the same guy
Malevolent Creation "Retribution" and "Stillborn"
Burzum "Hviss Lyset Tar Oss" More for the inside artwork than the cover
Luciferion "Demonication"

But I actually like poorly drawn lp covers like Iron Angel and Raw Energy etc..

I dont think the Iron Angel cover is poor, that guy also did the Helloween Walls of Jericho cover, both are fine with me, especially the Helloween cover is cool
Something like Sepultura's Bestial Devastation is much worse, although I think it still kicks asses

oh yeah also I want to add that Scott Stearns ("Necrodamus") does some pretty sick shit, that style is quite cool, (some might know him from Nunslaughter's Waiting to kill christ artworks)

Yeah INRI is probably album with best cover that uses a band photo on front, just great
Way better than Sentence of Death ahah
Oh no wait, Sextrash's sexual carnage takes the cake hahah

Here also some more covers that I think are good which I forgot to mention cause I focussed too much on naming artists that did stuff I like:
Hellhammer "Apocalyptic Raids" and "Triumph Of Death"
Celtic Frost "Morbid Tales"
Poison "Into The Abyss"
Repugnant "Hecatomb"
Imperator "The Time Before Time"
Slaughter "Strappado"
Scepter "Im Going To Hell"
Toxic Holocaust "Evil Never Dies"
Grotesque "In The Embrace Of Evil"
Razor "Armed And Dangerous"
Witches Hammer any official release
Coroner "R.I.P." and "Punishment For Decadence" both versions
The Exploited "Troops Of Tomorrow"
NME "Unholy Death"
Slayer "Hell Awaits", "Reign In Blood" and "South Of Heaven"
Sodom first 3 records
Metallica first 4 records (especially Justice)
and eh..
maybe I will add more later ehe...